U.S. patent number 4,630,612 [Application Number 06/614,432] was granted by the patent office on 1986-12-23 for ultrasonic diagnostic apparatus.
This patent grant is currently assigned to Aloka Co., Ltd., Hayashi Electric Co., Ltd.. Invention is credited to Hiroji Matsumoto, Yasunori Miyake, Katsuhiko Nagasaki, Michio Ohno, Hitoshi Takeichi, Rokuroh Uchida.
United States Patent |
4,630,612 |
Uchida , et al. |
December 23, 1986 |
Ultrasonic diagnostic apparatus
Abstract
An ultrasonic diagnostic apparatus capable of providing a B-mode
tomographic image of and Doppler information on a moving member in
a living subject. The apparatus comprises a cursor setting device
which supplies a signal for displaying a cursor at a prescribed
position on a B-mode display, echo tracking circuits which cause
markers to track the image signals of a prescribed moving member at
optionally selected positions on the cursor, marker setting devices
for setting the initial positions of the markers, a synthesizer for
synthesizing and sending to the B-mode display a B-mode image
signal and marker image signals from the echo tracking circuits,
and a position measuring circuit for measuring the position of the
prescribed moving member on the cursor on the basis of the marker
image signals from the echo tracking circuits. The apparatus can
display a moving member, for example a blood vessel, within the
subject as a B-mode picture which tracks the position of the moving
member as it moves and can further electrically output the position
of the moving member. As a result, it is possible to electrically
store or process the position of the blood vessel. In particular,
the apparatus makes it possible to easily and accurately measure
blood vessels in the circulatory system, the amount of blood
flowing through such vessels, and the volume of internal
organs.
Inventors: |
Uchida; Rokuroh (Tokyo,
JP), Nagasaki; Katsuhiko (Tokyo, JP),
Miyake; Yasunori (Tokyo, JP), Ohno; Michio
(Kawasaki, JP), Takeichi; Hitoshi (Kawasaki,
JP), Matsumoto; Hiroji (Kawasaki, JP) |
Assignee: |
Aloka Co., Ltd. (Tokyo,
JP)
Hayashi Electric Co., Ltd. (Kanagawa, JP)
|
Family
ID: |
27302464 |
Appl.
No.: |
06/614,432 |
Filed: |
May 25, 1984 |
Foreign Application Priority Data
|
|
|
|
|
May 25, 1983 [JP] |
|
|
58-90765 |
May 25, 1983 [JP] |
|
|
58-90766 |
May 25, 1983 [JP] |
|
|
58-77587[U] |
|
Current U.S.
Class: |
600/441;
600/455 |
Current CPC
Class: |
A61B
8/06 (20130101); A61B 8/13 (20130101); G01S
15/8979 (20130101); G01S 7/52073 (20130101); A61B
8/488 (20130101) |
Current International
Class: |
A61B
8/06 (20060101); A61B 8/08 (20060101); G01S
7/52 (20060101); G01S 15/00 (20060101); G01S
15/89 (20060101); A61B 010/00 () |
Field of
Search: |
;128/660-663
;73/821.25,625-626 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Howell; Kyle L.
Assistant Examiner: Jaworski; Francis J.
Attorney, Agent or Firm: Koda and Androlia
Claims
What is claimed is:
1. An ultrasonic diagnostic apparatus comprising an ultrasonic
probe which transmits and receives an ultrasonic wave signal to and
from a portion under examination which includes a moving member, a
transmission and reception circuit coupled to said ultrasonic probe
for controlling the pulse transmission and reception operation of
the ultrasonic probe, a B-mode display for displaying a B-mode
tomographic image in accordance with an ultrasonic B-mode image
signal received from the transmission and reception control
circuit, a cursor setting device for supplying to the transmission
and reception control circuit a cursor position signal in order to
display a cursor at a desired scan position of the B-mode display,
at least one echo tracking circuit coupled to said B-mode display
for causing at least one marker to track the video signal of the
moving member at a desired position on the cursor in response to
the receipt of an initial marker signal, at least one marker
setting device for supplying to the echo tracking device said
initial marker signal for setting the initial position of the
marker on the cursor, a synthesizer coupled to said transmission
and reception control circuit and said echo tracking circuit for
synthesizing and sending to the B-mode display the B-mode image
signal from the transmission and reception control circuit and the
marker image signal from the echo tracking circuit, and a position
measuring circuit coupled to said echo tracking circuit for
measuring the position of the moving member on the cursor in
accordance with the marker image signal from the echo tracking
circuit.
2. An ultrasonic diagnostic apparatus as claimed in claim 1 wherein
the ultrasonic pulse probe is an electronic linear scanning
probe.
3. An ultrasonic diagnostic apparatus as claimed in claim 1 wherein
the transmission and reception control circuit comprises a B-mode
oscillator which produces an ultrasonic excitation frequency for
the vibrators of the ultrasonic probe and this excitation frequency
is frequency divided to obtain a prescribed frequency and in
response thereto the ultrasonic probe is electronically scan
controlled.
4. An ultrasonic diagnostic apparatus as claimed in claim 1 wherein
the transmission and reception control circuit comprises an image
memory into which the received signals from the transmission and
reception control circuit are sequentially written until one frame
of the image has been stored therein, whereafter the stored data is
read out at high speed as a B-mode image signal.
5. An ultrasonic diagnostic apparatus as claimed in claim 1 wherein
the echo tracking circuit comprises a phase comparator and a
voltage controlled delay circuit, the phase comparator for
comparing the image signal initially set by the marker on the
cursor with the output of the voltage controlled delay circuit and
for controlling the output phase of the voltage controlled delay
circuit so as to maintain the two signals in coincidence with each
other at all times.
6. An ultrasonic diagnostic apparatus comprising an ultrasonic
probe which transmits and receives an ultrasonic wave signal to and
from a portion under examination which includes a moving member, a
transmission and reception circuit coupled to said ultrasonic probe
for controlling the pulse transmission and reception operation of
the ultrasonic probe, a B-mode display for displaying a B-mode
tomographic image in accordance with an ultrasonic B-mode image
signal received from the transmission and reception control
circuit, a cursor setting device for supplying to the transmission
and reception control circuit a cursor position signal in order to
display a cursor at a predetermined scan position of the B-mode
display, at least one echo tracking circuit coupled to said B-mode
display for causing at least one marker to track the video signal
of the moving member at a desired position on the cursor in
response to the receipt of an initial marker signal, at least one
marker setting device for supplying to the echo tracking device
said initial marker signal for setting the initial position of the
marker on the cursor, a synthesizer coupled to the transmission and
reception control circuit and said echo tracking circuit for
synthesizing and sending to the B-mode display the B-mode image
signal from the transmission and reception control circuit and the
marker image signal from the echo tracking circuit, a position
measuring circuit coupled to said echo tracking circuit for
measuring the position of the moving member on the cursor in
accordance with the marker image signal from the echo tracking
circuit, a Doppler probe for transmitting and receiving a
continuous ultrasonic wave to and from the portion under
examination, a flow velocity detection circuit coupled to said
Doppler probe for detecting the flow velocity of a fluid in the
moving member in accordance with the received signal from the
Doppler probe, an arithmetic processing circuit for computing the
flow amount of the fluid in the moving member from the position
signal from the position measuring circuit and the flow velocity
signal from the flow velocity detection circuit, and a display
coupled to said arithmetic processing circuit for displaying the
result of the computation by the arithmetic processing circuit,
whereby the flow velocity and flow amount of the fluid in the
moving member can be displayed in real time simultaneously with a
B-mode image of the portion under examination including the moving
member.
7. An ultrasonic diagnostic apparatus as claimed in claim 6 wherein
the ultrasonic pulse probe is an electronic linear scanning
probe.
8. An ultrasonic diagnostic apparatus as claimed in claim 6 wherein
the transmission and reception control circuit comprises a B-mode
oscillator which produces an ultrasonic excitation frequency for
the vibrators of the ultrasonic probe and this excitation frequency
is frequency divided to obtain a prescribed repeat frequency and in
response thereto the ultrasonic probe is electronically scan
controlled.
9. An ultrasonic diagnostic apparatus as claimed in claim 6 wherein
the transmission and reception control circuit comprises an image
memory into which the received signals from the transmission and
reception control circuit are sequentially written until one frame
of the image has been stored therein, whereafter the stored data is
read out at high speed as a B-mode image signal.
10. An ultrasonic diagnostic apparatus as claimed in claim 6
wherein the echo tracking circuit comprises a phase comparator and
a voltage controlled delay circuit, the phase comparator for
comparing the image signal initially set by the marker on the
cursor with the output of the voltage controlled delay circuit and
for controlling the output phase of the voltage controlled delay
circuit so as to maintain the signals in coincidence with each
other.
11. An ultrasonic diagnostic apparatus as claimed in claim 6
wherein the computation timing of the arithmetic processing circuit
is controlled in synchronism with a biological signal from the
subject.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an ultrasonic diagnostic apparatus, more
particularly to an improved ultrasonic diagnostic apparatus which
enables noninvasive observation and examination of an afflicted
portion of the circulatory system or of other tissue within the
body.
2. Description of the Prior Art
The art of using ultrasonic waves in the diagnosis of diseases of
the circulatory system has been practically applied in a wide range
of fields. Ordinarily, ultrasonic examination of the circulatory
system has fallen into two main categories: the method involving
the imaging of various organs and the method involving the
measurement of the flow velocity of blood and other body fluids.
The former of these methods has been widely used to produce
tomographic images of the heart, arteries and veins using A-mode
imaging, B-mode imaging or a modification of one of these modes. In
the latter method, ultrasonic waves are directed into the blood
flow and the blood flow velocity is determined using the Doppler
effect. This method is highly effective as a non-invasive means for
early discovery of diseases of the circulatory system of the brain,
for treatment of such diseases and for evaluation etc. of the
effect of medicines on the circulatory system of the brain.
In the former method, however, there have been disadvantages in
that the conventionally employed image display device permits
observation of only the tomographic image, making it necessary to
derive numerical values by measuring the displayed image and
complicating the diagnostic procedure, and in that it has been
difficult to electrically store the data derived by such
measurement together with the image. As a result, this method has
had ltitle practicability in actual diagnostic situations.
In particular, it has been extremely difficult to make accurate
measurement in cases where the object under observation includes a
moving member. Such a case arises, for example, in the examination
of the heart and other organs of the circulatory system where the
organ or the blood flowing through it are kept in constant motion
by the pulsation of the heart.
Moreover, although the conventional methods mentioned above wherein
an image is displayed through the use of an ultrasonic pulse beam
or the blood flow velocity etc. are measured using the Doppler
effect have been put to practical application in the examination of
the circulatory system, these two methods have been employed
independently of one another so that it has been impossible to
carry out realtime observation of the relationship between the
state of motion and the blood flow velocity in the actual portion
of the organ where motion occurs. As a consequence, it has not
always been possible to carry out an adeuate examination.
Another problem of the conventional methods concerns the importance
of knowing the amount of arterial blood flow, particularly that in
the brain circulatory system, in carrying out a proper diagnosis of
diseases of the brain circulatory system. For obtaining the amount
of blood flow with the conventional apparatuses, it has been
necessary to separately obtain the blood vessel diameter from an
A-mode image and the blood flow velocity by the Doppler effect and
then to carry out a separate calculation by, for example, a
computer. Te procedure is thus very complicated and is totally
incapable of providing appropriate real-time diagnostic
information. What is more, even the measurement of the diameter of
the blood vessel cannot be carried out with precision.
In this connection it is known that when the flow velocity of blood
etc. is to be measured using the Doppler effect of ultrasonic
waves, it is important to properly select the angle of ultrasonic
wave transmission and reception with respect to the direction of
blood flow, and that optimum results are obtained when, as shown in
FIG. 5, this angle is set at 60.degree..
In fact, however, it is generally impossible to determine the
direction in which a blood vessel runs within a living body so that
with the conventional apparatus the method used has been to attach
a Doppler probe to the surface of the body so as to form an angle
of approximately 60.degree. with respect to the presumed direction
of the blood vessel being subjected to measurement. As a result,
the conventional method of measuring blood flow velocity by the
Doppler effect has had the shortcoming of including a large error
factor.
SUMMARY OF THE INVENTION
In view of the comments and observations made in the foregoing, the
first object of the present invention is to provide an ultrasonic
diagnostic apparatus which is able to track the movement of a
moving member of the object under examination and display the
position thereof as a B-mode image and which is capable of
outputting said position as an electrical signal.
A second object of the invention is to provide an ultrasonic
diagnostic apparatus which is able to provide a real-time display
of the amount of blood flow in the circulatory system of the brain
at the same time as providing a tomographic image of the
corresponding blood vessel, for example, a carotid artery.
The third object of the invention is to provide an ultrasonic
diagnostic apparatus wherein the direction of transmission and
reception of a Doppler beam can be very easily set at any desired
angle with respect to the direction of flow in the region to be
examined.
These objects are obtained by providing an ultrasonic diagnostic
apparatus comprising an ultrasonic pulse probe which transmits and
receives an ultrasonic wave signal to and from a portion under
examination including a moving member, a transmission/reception
circuit for controlling the pulse transmission and reception
operation of the ultrasonic pulse probe, a B-mode display for
displaying a B-mode tomographic image on the basis of an ultrasonic
B-mode image signal obtained from the transmission/reception
control circuit, a cursor setting device for supplying to the
transmission/reception control circuit a cursor position signal in
order to display a cursor at a predetermined scan position of the
B-mode display, at least one echo tracking circuit for causing at
least one marker to track the video signal of the moving member at
a desired position on the cursor, at least one marker setting
device for supplying to the echo tracking device an initial marker
signal for setting the initial position of the marker on the
cursor, a synthesizer for synthesizing and sending to the B-mode
display the B-mode image signal from the transmission/reception
control circuit and the marker image signal from the echo tracking
circuit, and a position measuring circuit for measuring the
position of the moving member on the cursor on the basis of the
marker image signal from the echo tracking circuit.
Moreover to achieve the second object of this invention, there is
provided an ultrasonic diagnostic apparatus which, in order to
enable it to provide a real-time display of the flow velocity and
flow volume of a fluid in the moving member while at the same time
displaying a B-mode image of the portion under examination
including the moving member, comprises an ultrasonic pulse probe
which transmits and receives an ultrasonic wave signal to and from
a portion under examination including a moving member, a
transmission/reception circuit for controlling the pulse
transmission and reception operation of the ultrasonic pulse probe,
a B-mode display for displaying a B-mode tomographic image on the
basis of an ultrasonic B-mode image signal obtained from the
transmission/reception control circuit, a cursor setting device for
supplying to the transmission/reception control circuit a cursor
position signal in order to display a cursor at a predetermined
scan position of the B-mode display, at least one echo tracking
circuit for causing at least one marker to track the video signal
of the moving member at a desired position on the cursor, at least
one marker setting device for supplying to the echo tracking device
an initial marker signal for setting the initial position of the
marker on the cursor, a synthesizer for synthesizing and sending to
the B-mode display the B-mode image signal from the
transmission/reception control circuit and the marker image signal
from the echo tracking circuit, a position measuring circuit for
measuring the position of the moving member on the cursor on the
basis of the marker image signal from the echo tracking circuit, a
Doppler probe for transmitting/receiving a continuous ultrasonic
wave to/from the portion under examination, a flow velocity
detection circuit for detecting the flow velocity of a fluid in the
moving member on the basis of the pick-up signal from the Doppler
probe, an arithmetic processing circuit for commuting the flow
velocity of the fluid in the moving member from the position signal
from the position measuring circuit and the flow velocity signal
from the flow velocity detection circuit, and a display for
displaying the result of the computation by the arithmetic
processing circuit.
Further, to realize the third object of this invention, there is
provided an ultrasonic diagnostic apparatus wherein the ultrasonic
pulse probe for producing the B-mode tomographic image and the
Doppler probe are integrated as a single unit,
transmitting/receiving vibrators provided in the ultrasonic pulse
probe and a transmitting vibrator and at least one receiving
vibrator provided in the Doppler probe are fixed in a prescribed
positional relation, the B-mode scanning plane and the Doppler beam
are disposed so as to approach and intersect at a desired depth in
the portion under examination, and the ultrasonic pulse probe and
the Doppler probe are driven by ultrasonic excitation pulses and a
continuous wave, respectively, the two excitations being at
different frequencies, whereby the angle between the Doppler beam
and the direction of fluid flow in the portion under examination
can be set to a desired magnitude on the basis of the clarity of
the B-mode image.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram of one embodiment of the ultrasonic
diagnostic apparatus of this invention.
FIG. 2 is an explanatory view showing an example of a B-mode
tomographic image obtained with the ultrasonic diagnostic apparatus
of FIG. 1.
FIG. 3 is a block diagram showing a specific circuit arrangement
for the echo tracking circuit in the ultrasonic diagnostic
apparatus of FIG. 1.
FIG. 4 is diagram for explaining the operation of the echo tracking
circuit shown in FIG. 3.
FIG. 5 is an explanatory view showing the relation between the
direction of blood flow and the direction of the Doppler beam.
FIG. 6 is schematic view of one embodiment of an integrated probe
used in the present invention.
FIG. 7 is a plan view of the surface of a vibrator of the
integrated probe of FIG. 6.
FIG. 8 is a schematic view of another embodiment of an integrated
probe.
FIG. 9 is a plan view of the surface of a vibrator of the
integrated probe of FIG. 8.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Preferred embodiments of the invention will now be described with
respect to the drawings.
FIG. 1 shows the overall arrangement of the ultrasonic diagnostic
apparatus of the invention. The apparatus provides a B-mode image
display of a portion under examination of a subject 10 which
includes a moving member, namely in this embodiment a carotid
artery of the brain circulatory system, and at the same time
provides data on the blood vessel diameter, blood flow velocity and
blood flow volume relative to the carotid artery.
For the purpose of obtaining the B-mode display and measuring the
blood vessel diameter, blood flow velocity and blood flow volume, a
probe 12 is attached to the body of the subject 10 at a point in
the vicinity of one of the carotid arteries. The probe 12 of this
embodiment is an integrated probe including in a single unit an
ultrasonic pulse probe 14 for producing the B-mode display and a
Doppler probe 16 for detecting the blood flow velocity. The
ultrasonic pulse probe 14 directs ultrasonic pulses toward the
carotid artery and receives the echos reflected from the tissue
boundaries of the artery, making it possible to obtain a luminance
display of the tissues in the direction of depth on a CRT or other
display device and, by scanning the transmitted/received pulse wave
along a desired cross section, to obtain a desired B-mode
tomographic image. In the embodiment, the ultrasonic pulse probe 14
is constituted as an electronic linear scanning probe. On the other
hand, the Doppler probe 16 comprises a transmitting vibrator for
directing a continuous ultrasonic wave into the carotid artery and
a receiving vibrator for receiving the reflected wave which has
been frequency shifted by the Doppler effect in accordance with the
blood flow velocity in the carotid artery. The flow velocity of the
blood in the carotid artery can be derived from this frequency
shift.
B-mode image display
An explanation will first be given of the B-mode image display
employing the ultrasonic pulse probe 14.
The transmission and reception of the ultrasonic pulse beam from
the ultrasonic pulse probe 14 is controlled by a
transmission/reception control circuit 18 which conducts electronic
linear scanning control and also controls the focusing operation of
the ultrasonic pulse beam as required.
The transmission/reception control circuit 18 includes a B-mode
oscillatory 20 for producing an excitation signal of a frequency
appropriate for the vibrator of the probe 14. This fundamental
frequency from the B-mode oscillator 20 is subjected to
predetermined frequency division in a scanning controller 22
thereby to obtain a repeat frequency (rate frequency) appropriate
for the ultrasonic pulse beam. Electronic scanning control is
carried out by means of this repeat frequency. Actual
transmission/reception control of the probe 14 is carried out by a
transmission/reception device 24 which operates in response to the
repeat frequency from the scanning controller 22. The
transmission/reception device also carries out focusing control of
the pulse beam each time it is transmitted or received.
The pick-up signals obtained from the probe 14 are subjected to
focusing control, together with a specific amount of delay, by the
transmission/reception device 24 and, after being amplified and
detected, are sequentially stored at specific addresses in an image
memory 26 which may, for example, be a frame memory. This storage
operation is controlled by a write-in control circuit 28 and a
control signal from the scanning controller 22.
With this arrangement, once a given number of scans have been
completed so as to store the image of a single scanning frame in
the image memory 26, the stored data is read out at high speed by a
read-out signal from a standard TV synchronizing signal generator
30. The read-out signal is used as a B-mode image signal.
In this embodiment, this B-mode image signal is synthesized with
the synchronizing signal from the standard TV synchronizing signal
generator 30 in a synthesizer 32 to produce a synthesized image
signal which is forwarded to a B-mode display 36 constituted of a
CRT etc. where it is displayed as a tomographic image along a
specific scanning cross section.
Thus, in accordance with this embodiment, the B-mode pick-up signal
from the probe 14 is first once stored in the digital image memory
26, and the read-out of the stored data on the read-out side is
controlled by a TV synchronizing signal which is independentof the
write-in side. Thus, the sweep speed in the display can be made
many times faster than the ultrasonic scanning speed for write-in
to the image memory 26 so that it is possible to obtain an
ultrasonic tomographic image on the display 36 which is of high
quality and free of flicker.
FIG. 2 shows one example of an image displayed on the B-mode
display 36. The image shown is that obtained when the ultrasonic
pulse beam is transmitted/received perpendicularly to the carotid
artery. It will be noted that the carotid artery 100 is displayed
as a tomographic image in which both the inner and outer walls of
the artery appear with high clarity.
Measurement of blood vessel diameter
As is clear from the foregoing description, the apparatus according
to this invention makes it possible to obtain a high-clarity B-mode
tomographic image of the portion under examination (a carotid
artery) on the display 36. However, if at the same time as
observing this tomographic image it is also desired to observe the
corresponding amount of blood flow, it will be indispensable to
measure the inside diameter of the artery 100. In conventional
apparatuses, this inner diameter is determined by measurement from
an A-mode picture. In the present invention, however, it can be
measured automatically. What requires attention in the measurement
of the artery diameter is that the diameter of the artery 100
changes with the constant, alternate expansion and contraction
thereof with the pulsation of the circulatory system, making it
necessary to carry out the measurement while following the
variation in diameter without delay.
In FIG. 2 the reference numerals 102a and 102b denote the positions
of the inner wall of the artery 100 at the time of expansion and
contraction, respectively. In this invention, this movement is
tracked using the echo tracking method.
More specifically, as shown in FIG. 2, a cursor 104 is displayed
within the image appearing on the display 36 so as to pass through
approximately the center of the artery 100 and two markers 106 and
108 are made to appear at the two points of intersection of the
cursor 104 with the inner wall 102 of the artery 100. Thus, if it
should be possible to have these markers track the movement of the
inner wall 102, it would be possible to automatically determine the
diameter of the artery from the distance between the markers 106
and 108.
In this embodiment, the cursor 104 is established by having the
scanning controller 22 supply to the image memory 26, separately
from the pick-up signal from the probe 14, a luminance signal with
respect to a specific scanning position. In this case, the position
of the cursor 104 is selectively determined by a cursor setting
device 38. In this embodiment, the cursor 104 is fixed at the
center of the displayed picture and in actual operation the
position of attachment of the probe 12 on the subject under
examination is selected so as to cause the image of the artery 100
to be centered on the cursor 104. If desired, it is of course also
possible to arrange for the cursor 104 to shift to the desired
position with respect to the B-mode image of the artery 100 after
this image has been displayed.
The present invention further provides an echo tracking circuit in
order to make it possible to display the markers 106, 108 at
positions corresponding to the inner wall 102 of the artery 100 and
to cause these markers to follow the movement of the inner wall. In
this particular embodiment, there are provided two echo tracking
circuits 40, 42, one for each of the markers. Both of the echo
tracking circuits 40, 42 are supplied with a luminance signal,
namely that along the cursor 104. Further, for setting the initial
position of the markers, the echo tracking circuits 40, 42 are
supplied with initial marker setting signals from marker setting
devices 44, 46, respectively. The outputs from the echo tracking
circuits 40, 42 are sent to a selection circuit 48 and then are
independently forwarded to the synthesizer 32 when the selection
circuit 48 receives a selection signal from the scanning controller
22. The selected signal is then sent to a position measuring
circuit 50 (to be described later) where the position of the moving
member (in this embodiment, the inner diameter of the artery 100)
is measured.
More specifically, in this embodiment, the output of the position
measuring circuit 50 is supplied to a printer 78 which prints out
the calculated result and is also supplied to the synthesizer 32
which, when required, simultaneously displays it with the B-mode
picture.
The details of the echo tracking circuits 40, 42 are shown in FIG.
3. As the two circuits are identical, only the arrangement of the
echo tracking circuit 40 for the marker 106 will be explained in
the following.
The echo tracking circuit 40 is basically a phase lock loop
circuit. The picture signal initially set by the marker 106 on the
cursor 104 is compared with the output of a voltage controlled
delay circuit (VCD) 54 in a phase comparator 52 and the phase of
the VCD 54 is adjusted to keep the two signals coincident at all
times. The output phase of the VCD 54 is controlled by the initial
marker setting signal from the marker setting device 44 and the
value of the output of a sawtooth wave generator 56, and the VCD 54
produces a delayed output consisting of a tracking gate pulse
having a pulse width which is one half the wavelength of the
ultrasonic excitation signal from the B-mode oscillator 20. In this
embodiment the delay of this output corresponds to the depth of the
inner wall 102 of the artery 100 from the outer surface of the
subject under examination and by having the VCD 54 vary this delay
time so as to track the movement of the inner wall, it is possible
by outputting this delay time to hold the marker 106 constantly on
the inner wall 102 of the artery 100. It is noted that the output
of the phase comparator 52 is fed to the VCD 54 through a low pass
filter 58.
FIG. 4 shows the operation of the echo tracking circuit 40. The
fundamental frequency of the ultrasonic pulse beam
transmitted/received by the ultrasonic pulse probe 14 is fixed by
the B-mode oscillator 20. As shown by the magnified view of a
single wave of this excitation signal shown in FIG. 4a, the phase
of the wave shifts from that shown by the solid line in the figure
toward that shown by the chain line as the position of the artery
100 shifts.
As mentioned above, the gate pulse produced by the VCD 54 (FIG. 4b)
of the echo tracking circuit 40 has a pulse width which is one half
the wavelength of the excitation signal wave. The marker 106 is in
advance positioned in the picture by the initial marker setting
signal from the marker setting device 44 so as to fall at one of
the two points of intersection between the cursor 104 and the inner
wall 102 of the artery 100 at the beginning of tracking. As a
result, the delay time represents the distance between the surface
of the subject and the marker position, whereby it will be
understood that the gate pulse of FIG. 4b is located at a picture
signal position corresponding to the inner wall on one end of the
cursor 104.
The phase comparator 52 compares the wave form shown in FIG. 4a
with the gate pulse shown in FIG. 4b and when this is integrated in
the low pass filter 58, then, in the case where the gate pulse b
accurately tracks the solid line of the wave form a, the integrated
portion indicated by hatching in FIG. 4c will be constituted of
equal positive and negative parts so that the output of the low
pass filter will be zero. As a result, the output of the comparator
by the comparison with the sawtooth wave will remain unchanged and
the delay time will also stay the same.
On the other hand, when the received wave shifts in the direction
of the chain line in FIG. 4a, the output of the low pass filter 58
becomes positive as shown in FIG. 4d, the delay time of the VCD 54
is reduced by the same extent and the gate pulse tracks so as to
make the integrated value of the received wave shown by the chain
line become zero. Therefore, the marker 106 appearing within the
picture as shown in FIG. 2 constantly tracks the inner wall, while
the integrated value at this time is output as a signal indicating
the distance of the inner wall from the surface of the subject.
In the present embodiment, two markers 106, 108 are provided at
diametrically opposite points on the inner wall and the display
signals for these markers and the depth data are sequentially
switched over and selected in the selection circuit 48 by the
selection signal from the scanning controller 22. Consequently, in
addition to reading the B-mode image signal including the signal
for the cursor 104 from the image memory 26, the synthesizer 32
also reads the data for the markers 106, 108 appearing on the
cursor 104 from the selection circuit 48 and synthesizes these
signals for display on the display 36. Thus it is possible to
display a cross sectional view of the carotid artery including
markers that constantly track the inner wall of the artery as shown
in FIG. 2. Moreover, as mentioned above, the difference between the
positions of the two points of the inner wall indicated by the
markers is calculated by the position measuring circuit 50, whereby
it is possible to output the constantly changing diameter of the
artery as it changes from instant to instant.
Detection of blood flow velocity
A continuous untrasonic excitation wave is supplied to the
transmitting vibrator of the Doppler probe 16 from a Doppler
oscillator 60 and the continuous ultrasonic wave is transmitted
from the surface of the probe to pass through the carotid artery or
other blood vessel. As a result, in the present invention, it is
not only possible to obtain partial velocity information as in
ordinary pulse Doppler systems but also possible to detect the
average flow value over the whole area for each instant. Moreover,
as the frequency of the continuous wave produced by the Doppler
oscillator 60 differs from that of the ultrasonic pulses for B-mode
image display, there is also the advantage that it is possible to
measure both simultaneously.
The continuous ultrasonic wave is reflected by the blood,
particularly by the erythrocytes, flowing in the blood vessel and
is subject to the Doppler effect in proportion to the flow
velocity. The reflected wave which has been frequency shifted by
the Doppler effect is received by the receiving vibrator provided
in the Doppler probe 16 and the resulting signal is electrically
processed by a Doppler processing circuit 62. The Doppler
processing circuit 62, which includes a high frequency amplifier
64, a detector 66 and a band pass filter 68, extracts only the
blood flow velocity signal and sends this to a flow velocity
detection circuit consisting of a frequency/voltage conversion
circuit, where the Doppler beat, which is proportional to the blood
flow velocity, is converted to a voltage signal.
In this way, the blood flow velocity is detected in real time by
means of the Doppler effect.
Measurement of flow amount
As is clear from the foregoing explanation, the diameter of the
blood vessel can be obtained from the position measuring circuit 50
and the blood flow velocity can be obtained from the flow velocity
detection circuit 70. These two values are input to an arithmetic
processing circuit 72 which carries out a prescribed calculation
whereby it is possible to electrically obtain the amount of blood
flow at each instant. As the arithmetic processing circuit 72 it is
possible to employ a microprocessor and, moreover, it is also
possible to have the processing operations of the position
measuring circuit 50 and the flow velocity detection circuit 70
carried out by the arithmetic processing circuit 72. The arithmetic
processing circuit 72 is capable of sequentially processing input
data in accordance with a prescribed processing cycle and in the
present embodiment this processing timing is controlled in
synchronism with a biological signal from the subject 10, and for
this there is used the ECG (electrocardiogram) signal from the
subject 10. More specifically, an ECG circuit 74 detects the pulse
of the subject 10 and produces an ECG signal which controls a
processing trigger circuit 76 in such a way that it supplies
trigger signals to the arithmetic processing circuit 72 in
synchronism with the pulse of the subject 10. The computation of
the blood flow amount is carried out with this timing.
The signal representing the amount of blood flow is sent to the
printer 78 for print-out and is also simultaneously displayed on
the B-mode display 36 via a graphic display memory 79. It can also
be displayed on a graphic display separate from the B-mode display
36.
Further, it is also possible to provide the B-mode display 36 with
two screens and display the blood flow amount data and other
information on a separate screen from the screen for ordinary image
display.
Structure of the probe
With the arrangement described above it is possible to observe and
examine a desired moving member as a B-mode tomographic image while
also observing the amount of fluid flowing through the same member
by dint of a real-time computation of said flow amount. One aspect
of this invention that enhances this capability is the probe 12,
which is designed to facilitate the proper transmission into and
reception from the portion under examination of the ultrasonic
waves for B-mode image display and for Doppler detection. A
preferred embodiment of this probe will now be described below.
It is well known that when the flow velocity of blood or other
fluid is to be measured by a method employing the Doppler effect,
the angle of the ultrasonic wave to the direction of flow is a
critical factor and that, as shown in FIG. 5, the best results are
obtained when this angle is 60.degree..
In general, however, it is not possible to judge the direction in
which a blood vessel lies in a living body. With the conventional
apparatuses it has been only possible to presume the direction of
the blood vessel to be subjected to measurement and then to attach
the Doppler probe to the subject so as to form an angle of
approximately 60.degree. relative to this presumed direction. As a
result, the conventional apparatuses have had the drawback of
entailing a large error component in the measurement of the blood
flow velocity using the Doppler effect.
The probe 12 used in the present invention is illustrated in FIGS.
6 and 7. The probe 12 comprises both the ultrasonic pulse probe 16
for producing the B-mode tomographic image and the Doppler probe 16
for measurement of the blood flow velocity as integrated into a
single unit. This probe 12 is attached at the desired position on
the body of the subject 10 and is used to transmit/receive an
ultrasonic pulse beam and an ultrasonic continuous wave to/from a
blood vessel 100, typically a carotid artery.
In this embodiment the ultrasonic pulse probe 14 is constituted as
an electronic linear scanning probe and, as shown in FIG. 7,
comprises a plurality of ceramic vibrators 80 arranged in a single
row. By electronically scanning these ceramic vibrators it is
possible to carry out tomographic scanning in a manner cutting
across the artery 100. The scanning width of the row of vibrators
80 is therefore made greater than the diameter of the artery
100.
In this embodiment, the vibrators 80 of the ultrasonic pulse probe
14 are supplied with ultrasonic excitation pulses of a frequency of
5 MHz.
On the other hand, the Doppler probe 16 comprises a transmitting
vibrator 82 and a receiving vibrator 84 located in close
juxtaposition. In this embodiment, the transmitting vibrator 82 is
driven by a continuous ultrasonic excitation wave of a frequency of
7.5 MHz and the continuous ultrasonic wave directed into the
subject 10 is reflected by the blood (particularly the
erythrocytes) flowing in the artery. The reflected ultrasonic wave,
which is frequency shifted by the Doppler effect to an extent which
is proportional to the blood flow velocity, is then electrically
picked up by the receiving vibrator 84,
In this embodiment, the transmitting vibrator 82 and the receiving
vibrator 84 are fixed so as to form angles with the direction of
blood flow of 70.degree. and 60.degree. at the time the direction
of transmission/reception of the ultrasonic pulse beam is set
perpendicular to the direction of blood flow.
As in this embodiment the ultrasonic pulse probe 14 for B-mode
display and the Doppler probe 16 for measurement of blood flow
velocity are integrally formed as a single unit in the probe 12,
the probes 14 and 16 are held in a fixed positional arrangement,
making it possible for them to cooperate most effectively in
carrying out B-mode imaging and Doppler detection.
This will now be explained in more detail. As was mentioned earlier
with respect to FIG. 2, the B-mode image obtained from the
ultrasonic pulse probe 14 is displayed on a screen as a cross
section of the artery 100. And at this time the portion of the
subject 10 through which the Doppler beam from the Doppler probe
passes is substantially the same portion of the artery as that
displayed on the screen as shown in FIG. 2. Therefore, if the cross
section displayed as a B-mode image is perpendicular to the
direction of blood flow, the Doppler beam will automatically be
transmitted and received at the proper angle with respect to the
direction of blood flow. As a result, the measured blood flow
velocity obtained by the Doppler effect will accurately represent
the actual blood flow velocity in the artery 100.
One feature characterizing the present invention is that the cross
section of the artery 100 is displayed as a B-mode image. As is
well known, in the case of B-mode imaging, the image of highest
clarity is obtained when the ultrasonic pulse beam is
transmitted/received perpendicularly to the plane of the tissue
boundary in the subject. This of course applied as well to the wall
of the artery 100.
Therefore, in positioning the probe 12 on the subject 10, the
operator of the apparatus according to this invention need only
observe the B-mode image displayed as shown in FIG. 2 while
adjusting the position of the probe to obtain the tomographic image
of the artery 100 of highest clarity. This will assure that the
pulse beam is accurately directed perpendicularly to the artery 100
and that, as a natural result, the vibrators 82, 84 of the Doppler
probe which are fixed in a predetermined positional relation with
respect to the ultrasonic pulse probe 14 are oriented properly with
respect to the direction of blood flow in the artery 100. The blood
flow velocity reading obtained at this time can be used without
compensation as the final measured value.
Consequently, the present invention has merits in that the blood
flow velocity can be measured with little error and that the
attachment of the probe 12 can be carried out very easily
From the foregoing it will be understood that in accordance with
the present invention the proper positioning of the probe can be
accurately determined with reference to the clarity of the B-mode
image, which in turn makes it possible to greatly enhance the
precision with which the blood flow velocity can be measured by use
of the Doppler effect. Moreover, as any possible interference
between the ultrasonic pulse probe and the Doppler probe is
precluded by providing them with separate driving frequency
sources, it is possible to carry out transmission and reception
with both probes simultaneously, thus making it possible to obtain
both the B-mode image and the blood flow velocity in real time.
FIGS. 8 and 9 show another embodiment of a probe integrally
combining an ultrasonic pulse probe and a Doppler probe in a single
unit. Here like members to those shown in FIGS. 6 and 7 are denoted
by like reference numerals and no further explanation of these
members will be given.
The probe of this embodiment is characterized in that the Doppler
probe 16 is provided with two receiving vibrators. Namely,
receiving vibrators 84 and 86 are provided on opposite sides of the
transmitting vibrator 82 each at a prescribed distance therefrom.
The wave reflected from the artery 100 is received simultaneously
by both of the receiving vibrators 84, 86. The angles formed by the
vibrators 82, 84 and 86 with respect to the direction of blood flow
are selected as 66.degree., 76.degree. and 56.degree..
By provision of the two receiving vibrators 84, 86 it is possible
to reduce the adverse effect that would arise should the angle
between the direction of ultrasonic Doppler beam
transmission/reception and the direction of blood flow vary from
the well-known optimum angle of 60.degree.. Moreover, similarly to
the case of the preceding embodiment, the fact that the Doppler
probe 16 and the ultrasonic pulse probe 14 are combined in a single
unit makes it possible to realize highly accurate measurement of
the blood flow velocity by selecting the position of attachment of
the probe 12 so as to obtain a B-mode image of optimum clarity.
EFFECT OF THE INVENTION
With the ultrasonic diagnostic apparatus as described in the
foregoing, a cursor can be displayed at a prescribed scanning
position of a B-mode picture, markers can be provided at the points
of intersection between the cursor and a prescribed moving member
under examination, these markers can be made to track the movement
of the moving member, as a result the position of the moving member
can be displayed on a B-mode picture and can also be output
electrically, and as a further result the position of the moving
member can be electrically stored or arithmetically processed, so
that the apparatus has particularly high utility in the measurement
of blood vessel diameter or blood flow amount in the circulatory
system and, in the measurement of the volume of internal organs
etc.
Moreover, in accordance with the apparatus of the present
invention, it is possible to combine the results of the B-mode
image display with the results of the measurement of the blood flow
velocity using the Doppler effect of a continuous ultrasonic wave
to obtain an accurate real-time reading of the amount of blood flow
in a given portion of a subject under examination. As the apparatus
is thus able to measure the amount of blood or other fluid flowing
in the subject with high precision, it is especially useful for
obtaining optimum diagnostic information with respect to the
circulatory system.
Further, in accordance with this invention, an ultrasonic pulse
probe for B-mode imaging and a Doppler probe are integrated in a
single body so that the B-mode scanning plane and the Doppler beam
will approach and intersect at a desired depth in the portion under
examination. Because of this arrangement, it is possible to set the
angle between the direction of Doppler beam transmission/reception
and the direction of fluid movement within a moving member at a
desired magnitude, making the apparatus of this invention highly
useful for the measurement of flow velocity and the like.
Although in the embodiments described above, the measurements were
described as being carried out with respect to blood, the present
invention is not limited to measurement and imaging related to
blood and blood vessels and can also be applied effectively to the
imaging of other organs and the measurement of the flow velocities
and flow amounts of other body fluids than blood.
* * * * *